Seeding a Stronger Concrete

So what do you with 661,386,840 pounds of leftover sunflower seed husks each year?

If you're Turkey, which generates that fibrous avalanche, you find new uses for them. And if you can find them a place in the world's most common building material, you've got a match made in sustainable construction heaven.

Turkish researchers are reporting such a match, using sunflower seed husk material as concrete filler. Not only does the technology use up some of that voluminous food waste, the researchers say, but the aggregate creates a concrete that is more resistant to cracking during freeze-thaw cycles.

syngenta.com

Sunflowers are an important crop in Turkey, used primarily to produce sunflower oil.

"Sunflower seed waste as lightweight aggregate in concrete production," an article forthcoming in the International Journal of Environment and Waste Management, explains the team's findings.

Better Crack Resistance

"The team demonstrated that the use of husks reduces the density of concrete, as well as boosting the material's resistance to cracking after exposure to icy then thawing conditions," the journal reports.

"Its physical and mechanical properties show that concrete produced with [sunflower seed husks] has great potential as a low-cost, lightweight building material."

The new technology comes from engineers Can Burak Sisman and Erhan Gezer of Namik Kemal University in Turkey.

They explain how the accumulation of unmanaged wastes from the food industry, especially in developing countries, is becoming increasingly problematic.

inhabitat.com

Concrete is the world's most common building material, and manufacturing is an energy-intensive process. Efforts have been underway to reduce its carbon footprint.

Part of the answer, the researchers say, is finding new applications for the waste in environmentally friendly materials and composites for the road-building and construction industries. Doing so could also help ease the rising cost and chronic shortages of conventional materials.

Engineers are thus being challenged to convert industrial wastes to replacements for certain materials.

Concrete Alternatives

The world's most common building material, concrete is also considered one of its most energy- and resource-intensive materials. Efforts have been underway for years to find ways to recycle and reuse the material.

In addition, waste rubber, glass powder, paper waste sludge and other products have all been tested as alternative concrete fillers and bulking agents. Any such addition or substitution can, of course, significantly affect the concrete's strength, density, water resistance and other physical properties.

Researchers tried various recipes of sunflower seed cement. The mixtures reduced unit but increased water absorption.

The Kansas team says the cellulosic ethanol byproducts could help replace some of the Portland cement used in making nearly seven billion cubic meters of concrete each year. Not coincidentally, Kansas is the largest wheat-producing state and generates millions of tons of byproducts.

Sunflower Power

Similarly, Turkey is the ninth largest sunflower producer in the world, generating almost a million metric tons (tonnes) of product from 584,000 hectares, most of which goes to manufacture sunflower oil.

That output generates about 300,000 tonnes of fibrous seed husk annually, the team says.

The team experimented with different formulations of seed husk in a concrete mix, in amounts ranging from 5 percent to 30 percent of the mix.

They produced concrete samples with a density of about 2,000 tonnes per cubic metre; the lowest density could be classified as "lightweight."

The bottom line: "Some samples had low compressibility suitable for construction use, although higher husk content meant the resulting concrete could be used only for insulation applications," the journal reported.

"The replacement of SSH dramatically reduced the unit weight, compressive strength, splitting tensile strength and freezing-thawing resistance, but it increased the water absorption rate after 28 and 90 days," the team said.

For now, the team suggests, sunflower seed concrete would be most suitable for the construction of agricultural buildings that are usually only one floor and do not to be as sufficiently load bearing as domestic or office buildings.

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